A gradation correcting apparatus disclosed in Japanese Published Patent Application No. Hei. 1-300773 has been known as a conventional gradation correcting apparatus. This gradation correcting apparatus relates to a black level correcting apparatus, and employs a feedback system in which a black level in a scanning period is detected, a difference between the black level and a pedestal level is outputted and passed through a low-pass filter to perform gain adjustment, and the black level is controlled so as to be equal to the pedestal level.
However, use of the feedback system causes a problem that much time might be required until the feedback system is oscillated or stabilized. On the other hand, white correction, i.e., the white-side expanding operation, has not conventionally been carried out, while a prior art as described above has been proposed with respect to black correction, i.e., correction of the black level.
The present invention is made to solve the above-described problems and has for its objects to provided a gradation correcting apparatus and method for performing white correction or black correction with stability, without using a feedback system, and a video display apparatus having the gradation correcting apparatus.